Slow-reacting

Acrylonitrile and its comonomers can be polymerized by any of the weU-known free-radical methods. Bulk polymerization is the most fundamental of these, but its commercial use is limited by its autocatalytic nature. Aqueous dispersion polymerization is the most common commercial method, whereas solution polymerization is used ia cases where the spinning dope can be prepared directly from the polymerization reaction product. Emulsion polymerization is used primarily for modacryhc compositions where a high level of a water-iasoluble monomer is used or where the monomer mixture is relatively slow reacting. 

For an efficient enzymatic DKR the following requirements must be fulfilled (i) the KR must be very selective ( > 20) (ii) the racemization must be fast (at least 10 times faster than the enzyme-catalyzed transformation of the slow reacting enantiomer, krac >10 kent-s) (hi) the racemization catalyst must not react with the product of the reaction (iv) the KR and the racemization must be compatible under the same reaction conditions. 

Slow-reacting substance of anaphylaxis (SRS-A) is a mixture of leukotrienes C4, D4, and E4. This mixture of leukotrienes is a potent constrictor of the bronchial ait-way musculature. These leukotrienes together with leukotriene B4 also cause vascular permeabifity and attraction and activation of leukocytes and ate important regulators in many diseases involving inflammatory or... 

Parker, C.W., Fishman, C.M. and Wedner, J.H. (1980). Relationship of biosynthesis of slow reacting substance to intracellular glutathione concentrations. Proc. Natl Acad. Sci. USA 77, 6870-6873. 

SOZ Serum-opsonized zymosan SP Sulphapyridine SR Systemic reaction sr Sarcoplasmic reticulum SRBC Sheep red blood cells SRS Slow-reacting substance SRS-A Slow-reacting substance of anaphylaxis STZ Streptozotocin Sub P Substance P... 

Shaking a slow-reacting mixture caused detonation, attributed to indium-catalysed oxidation of acetonitrile. 

Dealkoxycarbonylation of activated esters occurs classically under drastic thermal conditions [90]. It constitutes a typical example of a very slow-reacting system (with a late TS along the reaction coordinates) and is therefore prone to a microwave effect. The rate determining step involves a nucleophilic attack by halide anion and requires anionic activation, which can be provided by solvent-free PTC conditions under the action of microwave irradiation [91]. The above results illustrate the difficult example of cyclic /1-ketoesters with a quaternary carbon atom in the a position relative to each carbonyl group (Eq. 36). 

Conversely, when n-octyl bromide was used with the less reactive terephthalate species, which constitutes a slow-reacting system , the yield was raised from 20 to 84% under the action of microwaves compared with A, which can be attributed to a later TS along the reaction coordinates (Eq. 40). 

In the 1930s an unknown material was hypothesized that was proposed to cause a slow and sustained contraction of smooth muscle. It was named the slow reacting substance (SRS). By 1940 a similar substance was reported to be found in guinea pig lungs and was called the slow reacting substance of anaphylaxis (SRS-A). Over the next 40 years, while no one could isolate, characterize, or synthesize this mate-... 

Under these oxidation conditions, (S )-16a-f and (7 )-16a-f remain as part of the slow reacting enantiomers and can be obtained in high enantiomeric purity (90-100% ee) and 40-50% chemical yield when using the corresponding l-(+)-and d-( )-DIPT. It should be pointed out that 2.0-2.5 equivalents of TBHP is required to get 50% conversion. Otherwise, the reaction proceeds extremely... 

Many methods have been reported for the enantioselective synthesis of the remaining PG building block, the (J )-4-hydroxy-cyclopent-2-enone. For example, the racemate can be kinetically resolved as shown in Scheme 7-28. (iS )-BINAP-Ru(II) dicarboxylate complex 93 is an excellent catalyst for the enantioselective kinetic resolution of the racemic hydroxy enone (an allylic alcohol). By controlling the reaction conditions, the C C double bond in one enantiomer, the (S )-isomer, will be prone to hydrogenation, leaving the slow reacting enantiomer intact and thus accomplishing the kinetic resolution.20... 

SRS-A Lung tissue (Slow-reacting substance of anaphylaxis) Contraction of smooth muscle acidic polypeptide... 

Also, hydrogen peroxide indeed can be used at low temperatures in place of the slow-reacting analogous alkyperoxides often employed at normal temperature. Compound I can be thermally activated and converted into compound II thus, true substrates can be used like abortive compounds undergoing only part of the catalytic cycle, which then can be continued as desired by warming. 

Leukotrienes (LTA, LTB LTC, LTD, and LTE ) are synthesized from arachi-donic acid by a cascade of enzymes that include 5-lipoxygenase (5-LOX), 5-lipoxy-genase-activating protein (FLAP), and leukotriene C4 synthase (LTC synthase) (79,80). The leukotriene LTA is synthesized by 5-LOX in the first step and is an unstable precursor that is then enzymatically converted to LTB or LTC (80,81), which can subsequently be metabolized to LTD and LTE. LTC, LTD, and LTE are the components of the slow-reacting substance of anaphylaxis. These moieties, particularly LTC and LTD, are active forms of CysLTs that interact with the G protein-coupled cysteinyl leukotriene receptors (CysLtrl and CysLtr2) (70,81,82). Once engaged, the activated CysLtrs receptors stimulate the secretion of mucus and induce edema and bronchoconstriction (81). 

Leukotrienes increase capillary permeability and serve as chemotactic factors for neutrophil granulocytes. As "slow-reacting substances of anaphylaxis," they are involved in allergic reactions (p. 326) together with PG, they evoke the spectrum of characteristic inflammatory symptoms redness, heat, swelling, and pain. 

J. H. Kim and J. J. Thomas, Use of 4-(nitrobenzyl)pyridine (4-NBP) to test mutagenic potential of slow-reacting epoxides, their corresponding olefins, and other alkylating agents. Bulletin of Environmental Contamination and Toxicology, 1992, 49(6), 879-885. 

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